harmonize stringify_exception, various comments

Author: jakkdl

src/_pytest/_code/code.py

@@ -459,6 +459,32 @@ def recursionindex(self) -> int | None:
         return None
 
 
+def stringify_exception(
+    exc: BaseException, include_subexception_msg: bool = True
+) -> str:
+    try:
+        notes = getattr(exc, "__notes__", [])
+    except KeyError:
+        # Workaround for https://github.com/python/cpython/issues/98778 on
+        # Python <= 3.9, and some 3.10 and 3.11 patch versions.
+        HTTPError = getattr(sys.modules.get("urllib.error", None), "HTTPError", ())
+        if sys.version_info < (3, 12) and isinstance(exc, HTTPError):
+            notes = []
+        else:
+            raise
+    if not include_subexception_msg and isinstance(exc, BaseExceptionGroup):
+        message = exc.message
+    else:
+        message = str(exc)
+
+    return "\n".join(
+        [
+            message,
+            *notes,
+        ]
+    )
+
+
 E = TypeVar("E", bound=BaseException, covariant=True)
 
 
@@ -736,33 +762,14 @@ def getrepr(
         )
         return fmt.repr_excinfo(self)
 
-    def _stringify_exception(self, exc: BaseException) -> str:
-        try:
-            notes = getattr(exc, "__notes__", [])
-        except KeyError:
-            # Workaround for https://github.com/python/cpython/issues/98778 on
-            # Python <= 3.9, and some 3.10 and 3.11 patch versions.
-            HTTPError = getattr(sys.modules.get("urllib.error", None), "HTTPError", ())
-            if sys.version_info < (3, 12) and isinstance(exc, HTTPError):
-                notes = []
-            else:
-                raise
-
-        return "\n".join(
-            [
-                str(exc),
-                *notes,
-            ]
-        )
-
     def match(self, regexp: str | re.Pattern[str]) -> Literal[True]:
         """Check whether the regular expression `regexp` matches the string
         representation of the exception using :func:`python:re.search`.
 
         If it matches `True` is returned, otherwise an `AssertionError` is raised.
         """
         __tracebackhide__ = True
-        value = self._stringify_exception(self.value)
+        value = stringify_exception(self.value)
         msg = f"Regex pattern did not match.\n Regex: {regexp!r}\n Input: {value!r}"
         if regexp == value:
             msg += "\n Did you mean to `re.escape()` the regex?"
@@ -794,7 +801,7 @@ def _group_contains(
             if not isinstance(exc, expected_exception):
                 continue
             if match is not None:
-                value = self._stringify_exception(exc)
+                value = stringify_exception(exc)
                 if not re.search(match, value):
                     continue
             return True

src/_pytest/outcomes.py

@@ -77,8 +77,8 @@ def __init__(
         super().__init__(msg)
 
 
-# Elaborate hack to work around https://github.com/python/mypy/issues/2087.
-# Ideally would just be `exit.Exception = Exit` etc.
+# We need a callable protocol to add attributes, for discussion see
+# https://github.com/python/mypy/issues/2087.
 
 _F = TypeVar("_F", bound=Callable[..., object])
 _ET = TypeVar("_ET", bound=type[BaseException])

src/_pytest/python_api.py

@@ -787,6 +787,9 @@ def _as_numpy_array(obj: object) -> ndarray | None:
 
 
 # builtin pytest.raises helper
+# FIXME: This should probably me moved to 'src/_pytest.raises_group.py'
+# (and rename the file to 'raises.py')
+# since it's much more closely tied to those than to the other stuff in this file.
 
 
 @overload
@@ -1000,9 +1003,11 @@ def raises(
 
 
 # note: RaisesExc/RaisesGroup uses fail() internally, so this alias
-# indicates (to [internal] plugins?) that `pytest.raises` will
-# raise `_pytest.outcomes.Failed`, where
-# `outcomes.Failed is outcomes.fail.Exception is raises.Exception`
+#  indicates (to [internal] plugins?) that `pytest.raises` will
+#  raise `_pytest.outcomes.Failed`, where
+#  `outcomes.Failed is outcomes.fail.Exception is raises.Exception`
 # note: this is *not* the same as `_pytest.main.Failed`
-# note: mypy does not recognize this attribute
+# note: mypy does not recognize this attribute, and it's not possible
+#  to use a protocol/decorator like the others in outcomes due to
+#  https://github.com/python/mypy/issues/18715
 raises.Exception = fail.Exception  # type: ignore[attr-defined]

src/_pytest/raises_group.py

@@ -18,6 +18,7 @@
 import warnings
 
 from _pytest._code import ExceptionInfo
+from _pytest._code.code import stringify_exception
 from _pytest.outcomes import fail
 from _pytest.warning_types import PytestWarning
 
@@ -61,17 +62,6 @@
     from exceptiongroup import ExceptionGroup
 
 
-# this differs slightly from pytest.ExceptionInfo._stringify_exception
-# as we don't want '(1 sub-exception)' when matching group strings
-def _stringify_exception(exc: BaseException) -> str:
-    return "\n".join(
-        [
-            exc.message if isinstance(exc, BaseExceptionGroup) else str(exc),
-            *getattr(exc, "__notes__", []),
-        ],
-    )
-
-
 # String patterns default to including the unicode flag.
 _REGEX_NO_FLAGS = re.compile(r"").flags
 
@@ -141,6 +131,12 @@ def unescape(s: str) -> str:
     return re.sub(r"\\([{}()+-.*?^$\[\]\s\\])", r"\1", s)
 
 
+# These classes conceptually differ from ExceptionInfo in that ExceptionInfo is tied, and
+# constructed from, a particular exception - whereas these are constructed with expected
+# exceptions, and later allow matching towards particular exceptions.
+# But there's overlap in `ExceptionInfo.match` and `AbstractRaises._check_match`, as with
+# `AbstractRaises.matches` and `ExceptionInfo.errisinstance`+`ExceptionInfo.group_contains`.
+# The interaction between these classes should perhaps be improved.
 class AbstractRaises(ABC, Generic[BaseExcT_co]):
     """ABC with common functionality shared between RaisesExc and RaisesGroup"""
 
@@ -161,7 +157,6 @@ def __init__(
             if match == "":
                 warnings.warn(
                     PytestWarning(
-                        "session.shouldstop cannot be unset after it has been set; ignoring."
                         "matching against an empty string will *always* pass. If you want "
                         "to check for an empty message you need to pass '^$'. If you don't "
                         "want to match you should pass `None` or leave out the parameter."
@@ -251,10 +246,13 @@ def _check_check(
         self._fail_reason = f"check{check_repr} did not return True"
         return False
 
+    # TODO: harmonize with ExceptionInfo.match
     def _check_match(self, e: BaseException) -> bool:
         if self.match is None or re.search(
             self.match,
-            stringified_exception := _stringify_exception(e),
+            stringified_exception := stringify_exception(
+                e, include_subexception_msg=False
+            ),
         ):
             return True
 

testing/python/raises.py

@@ -261,12 +261,10 @@ def tfunc(match):
         pytest.raises(ValueError, tfunc, match="").match("match=")
 
         # empty string matches everything, which is probably not what the user wants
-        # FIXME: I have no clue what session.shouldstop is doing here
         with pytest.warns(
             PytestWarning,
             match=wrap_escape(
-                "session.shouldstop cannot be unset after it has been set; ignoring.matching against "
-                "an empty string will *always* pass. If you want to check for an empty message you "
+                "matching against an empty string will *always* pass. If you want to check for an empty message you "
                 "need to pass '^$'. If you don't want to match you should pass `None` or leave out the parameter."
             ),
         ):

testing/typing_raises_group.py

@@ -6,10 +6,19 @@
 
 from typing_extensions import assert_type
 
-from _pytest.raises_group import RaisesExc
-from _pytest.raises_group import RaisesGroup
+from _pytest.main import Failed as main_Failed
+from _pytest.outcomes import Failed
+from pytest import raises
+from pytest import RaisesExc
+from pytest import RaisesGroup
 
 
+# does not work
+assert_type(raises.Exception, Failed)  # type: ignore[assert-type, attr-defined]
+
+# FIXME: these are different for some reason(?)
+assert Failed is not main_Failed  # type: ignore[comparison-overlap]
+
 if sys.version_info < (3, 11):
     from exceptiongroup import BaseExceptionGroup
     from exceptiongroup import ExceptionGroup